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July 10, 1928. 1,676,990

A. H. MITTAG SYSTEM OF DI STRIBUTION Filed July 13. 1923 Inventor:

Albern H-Minnag;

9 His Aunorrnes.

Patented July 10, 1928.

UNITED STATES PATENT OFFICE.

ALBERT H. MITTAG, OF SCHENECTADY, NEW YORK, ASSIGNOR 110 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

SYSTEM OF DISTRIBUTION.

Application filed July 13, 1923. Serial No. 651,399.

My present invention relates to systems of electrical distribution in which it is de sired to change direct current of one voltage to direct current of another voltage.

In a copending application of Ernst F. W. Alexanderson, Serial No. 651,409, filed concurrently herewith, there is described a system of this type in which electric valves are employed for controlling the supply of direct current to the converting system.

In the operation of such a system with electric valvesthere are two requirements necessary for the most cfiicient and satisfactory operation. One of these is that the control means should be operated. in such a way that current will start to flow through.

one valve before it is completely interrupted in the preceding valve. ment is that the current should be controlled in such a way that substantially rectangular wave form impulses of current shall be supplied by each valve. \Vhen thermionic valves are employed the operation may also be improved by supplying to the control means substantially rectangular wave form impulses of voltage. I

The object of my invention is to provide means whereby the above mentioned operating requirements may be efficiently obtained.

The novel features which I believe to becharacteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 shows diagrammatically one circuit connection which may be employed in carrying myinvention into effect, and Fig. 2 shows a slight modification of one portion of the circuit connections.

I have indicated in Fig. 1 a system in which direct current from the mains 1 and is supplied through the plate circuits of the thermionic valves 3 and 4; to the primary winding 5 of a transformer having a secondary winding (3 the opposite terminals of which are connected to the anodes of a mercury rectifier 7. Direct current main 1 connected to the middle point 8 of winding 5 and main 2 is connected to the cathodes of the valves so that current impulses supplied Another -.requir eto the winding 5 by' the two valves flow in opposite directions throughawinding 5.

The valves are controlled in the desired manner by means of voltage applied to their grids whiclvare suppliedfrom the secondary winding 6. The connections f0!::tlli$ purpose include a transformemt) the primary of. which is connected across;,-the terminals of winding (3. The terminalsof the, secondary. of transformer 9 are connected to the grids of yalves 3 and4throughqresistances:10 and the. .mid point, of the, l'secondary of transformer.9, is connectedt0htbe cathodes of valves 3,.and 4 througlr a reactanee. 11;.and a res stance;12. w 1-.

A load circuit to which the. rectified .current from rectifier 7Yis'supplied-iis connected: from .the;middle point of secondary winding fi throughjthe load devicesv 13 to the cathode 14 ofrectifier.-=7.- Cutrent fonheating the cathodes ofv valves; 3 and-A may be supplied by meansmfatransfornit 15; the Primary of whichis connected-to. the teimi-' nals; of secondary winding 6.

.In starting the operatioir'of the system described, current mayfifirstt be supplied to the cathodes of valves 3'-and 4. ;from a battery 16, by means of the switch li. Direct current anay thenbe. supplied to the valves by. means of the switch 18 which is first closed upon contact 19inorderthat resistance 20 maybe included in 'series with the direct current-supply to prevent the building up of abnormally high voltages in the main transformer. The rectifier 7 may then be. started by sup'plying'the necessary starting voltages to the starting electrodes through the switch 21 and transformer 22. As soon as the apparatus has begun to operate switch 18 may be thrown to contact 23 to disconnect resistance 20, switch 17 may be thrown to the positionindicated to disconnect battery 16 and switch 21 opened.

-'Ihe frequency of the oscillations produced may be determined by means of a condenser 2i which is connected across a portion or the whole of, the primary winding 5. In the operation of a system of the type described it is necessary for ellicient and satisfactory operation that current should be allowed to start in one valve bcfore it is completely interrupted in the other valve. This requires that the positive voltages supplied to the grids of the valves should lead the voltages induced in the secondary G. The desired lead imvoltage. may bcsecured'by including a condenser-or other capacitance means in circuit with the pri mary..o 1" .transforment). In the arrangement' shown 'in Figl 1 thislcondenser 25 is connected to the circuit through a transformer 26 for the purpose of stepping down the current and thus permitting the use of a smaller condenser. z. .1 in order to secure the most satisfactory operation -of a system of fthe typehere involved it is necessaryi that momentary tluctu ations in the direct currenU-supplied during therpe-riOds-wlmnthe-current is beingtransferred from. one: valvefitoi another should bel'pre entedi' This may be accom plish'ed byinserting-a reaatanee' in series with the directcurrenta s'upplyf-which ab sorbsthe dilference ofp'ot'ential bet-ween the direct :cunrent 'supp'ly source an'd'th'e voltage across the transformer winding; plus the drop-in the valve.- This*reactance'ifor low: frequency use would have-"t'o be of the iro'n core. type and "i t subjected to direct azurrentr '-'saturation would have to he und i-1ly-'large."

It is .also desirable to -em'p loy-a reactance in the-outputcircuita-which r'eaetan'ee also, if subject todir ect current---'saturat ion,- would have to be larger-Ibis possible,- however,-

a asinglexore zto greatly" reduee tliefsizeTQ quired. Dhei=.t'w0 :reaetances are so wohntl that the: direct wu-rrent components o'f t-he two currents flowingneutra'lizeeac-h otherand. these-cu rrent components have no saturatingsetfect upon t-heyco'rer t T-he..system which I have-described especially. adapted for transforming"high voltage direct current to-dir'e-ctcurrent at' a lower voltage, but may-equally \vell---be':em-' ployed for producing== the opposite .,resu-lt-i It \villof course bcundcrstood-thatthe types-- of .valre and .retificr indicated I arepurelyillustrative -and that other equivalent types may equallywell beemployed. -T-he ratio between the voltage ofltheg direct-[current supply and the oltae supplied to thelload" \\'ill. be substantially equal to the-ratio of the urns inthe primary winding 5 tothe turns in.the secondary winding 6.-- I

In order to-obtain. the most satisfactory operation of the valves 3- ancl--t the eontrolling potentials. a.pplied-=- to the grids should also be of substantially rectangular .wave form. The potentials produced. be-.

tween the terminals of secondary .6 have thedesired wave form but the use of the-condenser 25 for obtaining. the desired angle oflead tends to'change the wave form so that the wave form of the potential applied to transformeuS) difi'ers materially from that desired. The irregularity in wave form thus introduced is however corrected by the reactance 11 in-the grid circuits so that the wave form applied to thegrids may be made-to be substantially the same as that produced attheterminalsof secondary (3.

In the arrangen'ient shown in Fig.2 the desired angle- 0f lead; is obtained-- by; connecting a iresistanee -29 and r e actance 30in series across the terminals of secondary (3 and connecting the primary of transformer 9 to the terminals of reactance 30.

I have usedthe ex'pression substantially rectangular wave form in this specification andin" the'claims which= f o llow's,{not in its strict -'geome'trical -sensebiit "to describea wave'which builds up to'its maxi-mumw'al-uedies-down 'muchfluiore rapidly th'ana sine wavefand h'as whiit is commonly'know-n hat, I claim as newand (lesireto secure by -Lctters' Patent of the United States is:

1: The comliination' in 'a systemx'-ofi e-lec-;' trical distribution ;of-ajsoiirce of-'direct currentlya prim aryttitiding connected to' sa' id sou rce l t'lirough electrica Ive} second-' 1 winding indifi'etiyefly' associated 'with source th rough" aa electrie valve a second 1 ary winding inductively associated"*i 'itlrsaid-primary-winding; means f0r-=controllin t-he -actiozr ofi-said valve to supplyto said primary winding 'substantially rectangular-'- wave form currentimpulses. and a circuit connection which includes -a' capac-itance for supplying to sa-idalve-control means from saidsecondary i winding variable voltagesthe p dueed in said secbndar-y-winding- 3(-T-he combination -in a system of elec'-' trical distribution of asource of directcur-= rent, a primary winding connected to said source throu'gh a plura-lit of electric valves;- a secondary w'i-nding in uctively associated with said primary-winding, meansfor-controlling-the act-iorrof said valves 'to producein said secondary winding substahtiallyreetangular wave form 'cu'rrentimpulses, andmeans for supplying tothe control means of said valves .fromi saidseconda-ry winding variable voltages, -the phase of which leads the. voltages induced in said secondary winding.

4. The combinationdn a system of elec trical distribution of a source of direct current; a primary winding; connected to said sourcethrouglran electric valve... a seeond-- any winding inductively asociated withsaid primarywinding,.and means=for controlling base -ofwhich leads the voltages in--- the action of said valve to supply to said primary winding substantially rectangular wave form current impulses and {or supplying to said valve control means from said secondary winding variable voltages the phase of which leads the voltages induced in said secondary winding.

5. The combination in a system of electrical distribution of a source of direct current, a primary winding connected to said source through a plurality of electric valves, a secondary winding inductively associated Withsaid primary winding, means for controlling the action of said valves to produce in said secondary winding substantially rectangular wave form current impulses, and means for supplying to the control means of said valves from said secondary winding variable voltages of substantially rectangular wave form, the phase of which leads the voltages induced in said secondary winding.

6. An electrical apparatus comprising direct current terminals, a transformer provided with primary and secondary windings, electrical valve means provided with a cathode and anode connected between one of said terminals and said primary winding and with a grid for controlling the current between said cathode and anode, a capacitance connected between said secondary winding and said grid, and means connected in circuit with said grid for neutralizing the effect of said capacitance on the wave form of the potential applied to said grid throu 11 said secondary winding.

7. n electrical apparatus comprising direct current terminals, a transformer provided with primary and secondary windings, electrical valve means provided with a cathode and anode connected between one of said terminals and said primary winding and with a grid for controlling the current between said cathode and anode. a capacitance connected between said secondary winding and said grid, and an inductance connected in circuit with said grid for neutralizing the effect of said capacitance on the wave. form of the potential applied to said grid through said secondary winding.

8. An electrical apparatus comprising direct current terminals, a transformer provided with primary and secondary windings, electrical valve elements provided with cathodes and anodes connected between one of said terminals and said primary Winding and with control grids, a condenser connected between said secondary winding and said grids, means connected in circuit with said grids for neutralizing the effect of said condenser on the wave form of the potential applied to said grids through said secondary winding, and means connected between said windings for neutralizing momentary fluctuations in the current supplied through said terminals when current is transferred from one valve to another.

9. An electrical apparatus comprising direct current terminals, a transformer provided with primary and secondary windings, electrical valve elements provided with cathodes aud anodes connected between one of said terminals and said primary winding and with control grids, a condenser connected between said secondary winding and said grids, means connected in circuit with said grids for neutralizing the efl'ect of said condenser on the wave form of the potential applied to said grids through said secondary winding, and inductive means connected between said windings for neutralizing momentary fluctuations in the current supplied through said terminals when current is transferred from one valve to another.

In witness whereof I have hereunto set my hand this 12th day of July, 1923.

ALBERT H. MITTAG. 

